Among all the problems encountered in the domain of thermobonding interlinings, one of the most delicate to solve consists of the risk of transpiercing the interlining support during the application of the thermobonding interlining by hot pressure against the piece of garment to be reinforced. In fact, the temperature which is chosen to effect this hot application must make it possible to effect fusion of the dot of polymer so that the polymer thus melted can spread and adhere on the surface fibers or filaments of the garment. However, it frequently happens that such distribution is not made solely on the surface, but that the polymer creeps through the fibers or filaments and appears on the opposite surface of the interlining support. This does not affect the aesthetics, unless the interlining is intended to be visible and to form the rear face of the garment. In any case, the effect of such transpiercing is to locally increase the rigidity of the interlining and therefore of the piece of garment, which may be contrary to the effect desired. It may also provoke adhesions on the lining fabrics, such as lining and parts of welting cloth, which is detrimental to the quality of the garment.
In order to solve this difficulty, it has already been proposed to produce a thermobonding interlining of which the dots of thermofusible polymer comprise two superposed layers, namely a first layer in contact with the face side of the interlining support and a second layer disposed precisely above the first. Of course, the constituents of the two layers are determined so that, when they are applied hot under pressure on the piece of garment, only the thermofusible polymer of the second layer reacts to the action of the temperature. In that case, the thermofusible polymer can only diffuse towards the piece of garment, being prevented from doing so towards the interlining support, the first layer acting to some extent as barrier.
In practice, this double-layer technique presents drawbacks, particularly the difficulty of effecting the superposition of the two layers and risk of delamination of the two layers.
In order to overcome these drawbacks, Applicants have already proposed, in document FR 2 606 603, employing means of chemical nature, acting on the thermofusible polymer with a view to modifying its chemical structure at least partially, at least at the interface with the interlining support, so as to prevent the thermofusible polymer from bonding through the interlining support under the effect of heat and/or pressure and/or vapour. The means, of chemical nature, adapted to modify the chemical structure of the thermofusible polymer comprise at least one reactive matter and at least one reactive means capable of stimulating, assuring and promoting the reaction between the reactive matter and the thermofusible polymer.
Different categories of reactive matters are explicitly cited, namely thermosetting products, carbamide resin, particularly urea-formaldehyde and malamine formaldehyde, simple molecules or polymers bearing at least one isocyanate function, blocked or not, simple molecules or polymers bearing at least one aziridine function, modified polymers bearing at least one reactive chemical function, particularly epoxy function or vinyl function.
Among the reactive means are cited additions of heat, ultraviolet radiation and electron bombardment. It is specified that this reactive means may be used in the presence of catalysts. More precisely, when the reactive means of the reaction of crosslinking of the thermofusible polymer and of the modified polymer with vinyl reactive function is UV radiation, it is provided that the latter intervenes with contacting of photoinitiator products.
Where the reactive means comprises electron bombardment, it is provided to add to the mixture of thermofusible polymer and of reactive matter a photoinhibitor agent in order to limit the propagation of the chemical reaction of modification. The interlining support coated with the mixture is passed in front of a photon or electron source located on the non-coated face of the support so that the particles preferably bombard the holes or perforations of the support, opposite the thermofusible polymer.
In practice, it has proved impossible to obtain satisfactory results under the conditions described in document FR 2 606 603, by using as reactive means an electron bombardment, despite all the interest that this technique presented. The difficulty of monitoring the propagation of the chemical reaction with the aid of photoinhibitor agents, and the difficulty of acting preferably at the level of the holes or perforations of the interlining support, opposite the thermofusible polymer, contribute to this failure.
It is an object of Applicants to propose a process for manufacturing a thermobonding interlining employing electron bombardment to modify the chemical structure of the thermofusible polymer, which overcomes the difficulties set forth hereinabove.